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Essential Question: What are the steps in the water cycle?

Key Concept: Water is always moving between the troposphere and surface of Earth. Each components of the water cycle process has certain conditions under which each form of precipitation develops.

Water ...Where is it?EVERYWHERE

97% of Earth's water is salt water3% is freshwater

...but much of this water is frozen.

The rest can be found in groundwater, lakes, wetlands, rivers, and water vapor in the atmosphere.

Water Cycle

A NEVER ENDING movement of water between Earth's surface and the atmosphere.

There are 3 REPEATING processes:- Evaporation

- Condensation- Precipitation

** This process could not happen without the sun's energy!

1. Evaporation: process that changes a liquid to a gas

- Heat energy from the sun causes water to change from a liquid to a gas.

-This gas is called water vapor. -Plants also release water vapor through transpiration

2. Condensation: a process that changes gas to a liquid - Water vapor changes back to water droplets when it cools.

Where: High Low On a surfaceMakes: Clouds Fog Dew

Clouds= condensed water vapor. **Frost forms when water vapor directly changes from a gas to an ice crystal. (This happens when the air temperature is at or below freezing)

3. Precipitation: water falls to Earth's surface as rain, snow, freezing rain, sleet, or hail. (Depends on weather conditions)

- Water vapor changes back to water droplets when it cools.

Water droplets form in clouds - when they get to big then they fall to the ground = rain/precipitation.

Precipitation brings water back to Earth.

**If this water is heated, it can become water vapor = cycle continues.

4 types of precipitation

http://earthguide.ucsd.edu/earthguide/diagrams/watercycle/index.html

When water falls to the ground, the water may flow over land and collect in:- rivers - streams - ponds -lakes

After it precipitates, water always attempts to move back towards sea level as SURFACE WATER FLOW or GROUND WATER FLOW

1. Surface water flow (Run off): water we can easily see moving across Earth's surface.

2. Ground water flow: water that soaks into the ground. Water falls through cracks/spaces between sand and soil. (porous soil = a lot of space in soil)-Water collects in aquifers underground.